Running win 10/WSL/Ubuntu reports missing dlls

[btipton-ds]

These messages appear in all my output logs now

--> FOAM Warning :
From function void* Foam::dlOpen(const Foam::fileName&, bool)
in file POSIX.C at line 1251
dlopen error : libfvMotionSolvers.dll: cannot open shared object file: No such file or directory

This is odd. It's expected that there should be no .dll files on a linux build - even under WSL.
Are these needed .so files mislabeled?
Deprecated libs?
blockMesh.log